The present invention relates to circuitry for sensing the presence or absence of parts along an assembly line in order to halt the progression of the assembly line if an abnormal condition occurs.
In assembly line manufacture of many items, part detectors have been utilized to determine whether certain parts have been properly made or installed. For example, in the manufacture of the tops for tab-top beverage containers on a transfer press or other production line, part-detecting mechanisms have been employed to detect whether the tab pull is in place. Sensors, such as grounding probes, descend to detect the presence or absence of the tab pull when the line is momentarily at rest, such as during a stamping step at a preceding station. It is critically important to detect whether the production is proceeding normally not only for quality control, but to assure there is no loose tab in the press which might damage dies or other expensive tooling.
Prior art control circuitry, which accepts inputs from the sensors, halts the transfer press if a probe fails to detect a part. Some controllers, such as the IC Series Malfunction Detectors made by Tyco Wintriss Controls, Garden City Park, New York 11040, may halt operation also after a sensor malfunctions for a continued period of time; but to the best of Applicant's information such shut down depends on time lapse and is not keyed directly to the stages of operation of the machine.